mirror of
https://github.com/django-q2/django-q2.git
synced 2026-09-15 13:37:56 +08:00
8b3d6b7d2a
Made `Broker` and `Queue` classes pickable which fixes the the problem with new default `spawn` proces start method.
82 lines
2.8 KiB
Python
82 lines
2.8 KiB
Python
"""
|
|
The code is derived from https://github.com/althonos/pronto/commit/3384010dfb4fc7c66a219f59276adef3288a886b
|
|
"""
|
|
import multiprocessing
|
|
import multiprocessing.queues
|
|
import sys
|
|
|
|
|
|
class SharedCounter:
|
|
""" A synchronized shared counter.
|
|
|
|
The locking done by multiprocessing.Value ensures that only a single
|
|
process or thread may read or write the in-memory ctypes object. However,
|
|
in order to do n += 1, Python performs a read followed by a write, so a
|
|
second process may read the old value before the new one is written by
|
|
the first process. The solution is to use a multiprocessing.Lock to
|
|
guarantee the atomicity of the modifications to Value.
|
|
|
|
This class comes almost entirely from Eli Bendersky's blog:
|
|
http://eli.thegreenplace.net/2012/01/04/shared-counter-with-pythons-multiprocessing/
|
|
"""
|
|
|
|
def __init__(self, n=0):
|
|
self.count = multiprocessing.Value("i", n)
|
|
|
|
def increment(self, n=1):
|
|
""" Increment the counter by n (default = 1) """
|
|
with self.count.get_lock():
|
|
self.count.value += n
|
|
|
|
@property
|
|
def value(self):
|
|
""" Return the value of the counter """
|
|
return self.count.value
|
|
|
|
|
|
class Queue(multiprocessing.queues.Queue):
|
|
""" A portable implementation of multiprocessing.Queue.
|
|
|
|
Because of multithreading / multiprocessing semantics, Queue.qsize() may
|
|
raise the NotImplementedError exception on Unix platforms like Mac OS X
|
|
where sem_getvalue() is not implemented. This subclass addresses this
|
|
problem by using a synchronized shared counter (initialized to zero) and
|
|
increasing / decreasing its value every time the put() and get() methods
|
|
are called, respectively. This not only prevents NotImplementedError from
|
|
being raised, but also allows us to implement a reliable version of both
|
|
qsize() and empty().
|
|
"""
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
if sys.version_info < (3, 0):
|
|
super(Queue, self).__init__(*args, **kwargs)
|
|
else:
|
|
super(Queue, self).__init__(
|
|
*args, ctx=multiprocessing.get_context(), **kwargs
|
|
)
|
|
self.size = SharedCounter(0)
|
|
|
|
def __getstate__(self):
|
|
return super(Queue, self).__getstate__() + (self.size, )
|
|
|
|
def __setstate__(self, state):
|
|
super(Queue, self).__setstate__(state[:-1])
|
|
self.size = state[-1]
|
|
|
|
def put(self, *args, **kwargs):
|
|
super(Queue, self).put(*args, **kwargs)
|
|
self.size.increment(1)
|
|
|
|
def get(self, *args, **kwargs):
|
|
x = super(Queue, self).get(*args, **kwargs)
|
|
self.size.increment(-1)
|
|
return x
|
|
|
|
def qsize(self) -> int:
|
|
""" Reliable implementation of multiprocessing.Queue.qsize() """
|
|
return self.size.value
|
|
|
|
def empty(self) -> bool:
|
|
""" Reliable implementation of multiprocessing.Queue.empty() """
|
|
return not self.qsize() > 0
|